Description of the Prior Art
Remote data units connected in the field along the path of a seismic data cable can have two separate types of connectors so that the cable connections thereto cannot be mixed up. That is, one connector of the data unit can be suitable for connection to the downstream connector of a cable segment arriving from the upstream side of the data unit and the other connection of the data unit can be suitable for connection to the upstream connector of a cable segment to be strung downstream to the next subsequent data unit.
However, it is not uncommon for the cables to be laid out prior to any connections or to be laid out by more than one person or crew from two or more different starting locations. When this happens using data units and cable segments having upstream and downstream connectors that differ from each other, it is frustrating to find out that one or more of the cable segments have been strung out in reverse for proper connection. Since a single cable segment between data units in many cases is over 100 yards long, it is not only frustrating, but it is also time consuming, and therefore expensive, to take up and re-lay cable segments that are originally incorrectly aligned. In some cases, the terrain also is rugged or otherwise difficult for the field personnel. Unnecessary cable manipulations are to be avoided if at all possible.
Therefore, it is desirable to have cable segments and remote data units that have universal connectors which cannot be mixed up. In such a case, it does not matter how the cables are oriented as far as their ends are concerned or how the cable segments are connected into the remote data units. The only problem is that the control or command signals from the master station, usually a seismic control and recording installation located in a tent or a truck, are designed to progress in one direction and the data signals transmitted from the data units to the master station are generally designed to progress in the opposite direction. Therefore, the universal connections have to have some provision for ensuring the proper direction alignment for the control and data signals. Means heretofore available for such purpose have been complex, unreliable and have generally required additional control operations. This adds to the difficulty, expense and reliability of data collection, which by its nature suffers enough from these difficulties.
Fiberoptics have had many uses where it is desirable to direct light along a path that may have turns on deviations from a straight line. The present invention utilizes fiberoptics in a unique application for ensuring that universal connections are properly made vis-a-vis the control and data paths through the remote data units in a seismic data cable connection system.
Therefore, it is a feature of the present invention to provide improved direction sensing apparatus in connection with a plurality of data stations and connecting cable connecting segments, each of the station and the cable segments having universal connectors.
It is another feature of the present invention to provide an improved direction sensing apparatus in a cable system having intermediate stations therealong, one end of which is connected to a master station, using fiberoptics within the cable system and light sources and detectors as the means for ensuring proper connections.